Some known sorts of metals have the characteristics of absorbing hydrogen and releasing hydrogen. Any of such metals absorbs hydrogen to become metal hydride; otherwise, hydrogen is released by the metal hydride, the metal hydride is back to the metal. For instance, the alloy of iron and titanium, the alloy of lanthanum and nickel, the alloy of magnesium and nickel, etc., those hydrogen storage alloys are found 1960-1970 of 20th century.
The prior arts to manufacture a high purified Mg2Ni alloy are vacuum arc melting, induction melting, powder metallurgy, laminate rolling, mechanical alloying, rotation-cylinder method, etc. Such prior arts have the disadvantages of expensive equipment, a long period of manufacturing, a less quantity of output, etc. Further, eutectic Mg+Mg2Ni and γ-phase Mg2Ni are easily mixed each other during manufacturing processes. Therefore, the high purified γ-phase Mg2Ni is hardly to gained.